Use of silylated beta-dicarbonyl compounds as halogenated polymer stabilisers

ABSTRACT

The invention concerns the use in a stabilizing composition for halogenated polymers, of at least a silylated compound of formula: (R1)4-x-Si[O—C(R2)=CH2-C(═O)(R3)]x, wherein R1, identical or different, represent an aliphatic or aromatic radical; said radicals being selected such that the silylated compound has a boiling point higher than at least 30° C. relative to the working temperature of said polymer; R3 represents an aliphatic radical R or a radical —OR1; R2, R and R1, identical or different, represent an aliphatic radical, linear or not, comprising 1 to 10 carbon atoms, or an aromatic radical, preferably comprising 6 carbon atoms, optionally substituted by at least an aliphatic radical comprising 1 to 10 carbon atoms; x is equal to 1 or 2.

The subject of the present invention is the use of silylatedβ-dicarbonyl compounds as stabilizers for halogenated polymers.

More particularly, the subject of the invention is silylated compoundswhich are derived from β-dicarbonyl compounds whose boiling point isless than or equal to, or even slightly greater than the workingtemperature of the halogenated polymers.

The β-dicarbonyl compounds, such as the β-diketones or the β-ketoesters, are well known stabilizers for halogenated polymers, such aspolyvinyl chloride.

Acetylacetone is an example of this type of compound. Indeed, itsboiling point is of the order of 140° C. This β-diketone is veryeffective but has the drawback of being volatile. However, in mostcases, the working temperatures of the halogenated polymers aresufficiently high for acetylacetone to evaporate and escape from thepolymeric composition.

In the case of β-dicarbonyl compounds whose boiling point is close tothe working temperature of the halogenated polymers, difficulties areonce again encountered. Indeed, in such cases, the vapor pressure ofcompound is very high, which is favorable to a loss of said β-dicarbonylcompound.

The object of the present invention is therefore to remedy theseproblems by providing a compound derived from a β-diketone or from aβ-keto ester which remains as effective as the initial β-diketone orβ-keto ester and which does not risk being eliminated from the polymericcomposition during the working of the latter.

These aims and others are achieved by the present invention whosesubject is therefore the use, in a stabilizing composition for ahalogenated polymer, of at least one silylated compound of the followingformula:(R¹)_(4-x)—Si[O—C(R²)═CH—C(═O)(R³)]_(x)in which formula

-   R¹, which are identical or not, represent an aliphatic or aromatic    radical; said radicals being chosen such that the silylated compound    has a boiling point at least 30° C. higher relative to the working    temperature of said polymer;-   R³ represents an aliphatic radical R or a radical —OR′;-   R², R and R′, which are identical or not, represent a linear or    nonlinear aliphatic radical comprising 1 to 10 carbon atoms, or an    aromatic radical, preferably comprising 6 carbon atoms, optionally    substituted with at least one aliphatic radical comprising 1 to 10    carbon atoms;-   x equals 1 or 2.

It has been observed, all else being equal, and in particular the molarquantity of β-dicarbonyl compound, that the coloration stability of ahalogenated polymer comprising such a silylated compound is enhancedrelative to the coloration stability of a polymer comprising the sameβ-dicarbonyl compound which is nonsilylated.

However, other characteristics and advantages will emerge more clearlyon reading the description which follows.

It should be noted that in what follows, the boiling points are thosemeasured at room temperature (20° C.) and at atmospheric pressure (10⁵Pa).

As was mentioned above, the stabilizing composition comprises at leastone compound of formula (R¹)_(4-x)—Si[O—C (R²)═CH—C(═O)(R³)]_(x).

In the above formula, as was indicated earlier, the radical R³ mayrepresent an aliphatic radical R; in this case, the compound is aβ-diketone. Alternatively, the radical R³ may represent a radical —OR′;in this case, the compound is a β-keto ester.

R², R and R′, which are identical or not, each represent a linear ornonlinear aliphatic radical comprising 1 to 10 carbon atoms, or anaromatic radical, preferably comprising 6 carbon atoms, optionallysubstituted with at least one aliphatic radical comprising 1 to 10carbon atoms.

By way of example of a linear or nonlinear aliphatic radical, there maybe mentioned alkyl radicals such as methyl, ethyl, propyl and itsisomers, butyl and its isomers, pentyl and isomers, hexyl and isomers.

As an aromatic radical, there may be mentioned in particular benzyl,phenyl, toluyl and xylyl.

It should be noted that said radicals are more particularly chosen sothat the β-diketone (or β-keto ester) from which the silylated compoundis derived, has a boiling point such that the difference between theworking temperature of said halogenated polymer and the boiling point ofsaid β-diketone (or of said β-keto ester) is less than 30° C. It isspecified that the difference between these two temperatures may bepositive or negative.

Advantageously, the radical R or the radical R′ represents an aliphaticradical, preferably an alkyl radical, comprising 1 to 10 carbon atoms.

According to a preferred embodiment of the invention, the radical R³represents an aliphatic radical R as defined above.

As for the radicals R¹, which are identical or not, they are first ofall chosen so that the silylated compound has a boiling point at least30° C. higher relative to the working temperature of said polymer.Preferably, the boiling point is higher by at least 60° C., and stillmore advantageously by at least 80° C.

More precisely, these radicals represent an alkyl radical comprising 1to 10 carbon atoms, or an aromatic radical comprising 6 carbon atoms,optionally substituted with at least one alkyl radical comprising 1 to10 carbon atoms.

By way of example, the radicals R¹, which are identical or not, arechosen from methyl, ethyl, propyl and isomers, butyl and isomers, pentyland isomers, hexyl and isomers, benzyl, phenyl, toluyl and xylylradicals.

Finally, the silylated compounds may comprise one molecule ofβ-dicarbonyl compound (x=1) or two molecules of β-dicarbonyl compound(x=2).

It should be noted that the stabilizing composition may comprise one ormore silylated compounds.

More particularly, the silylated compound entering into the stabilizingcomposition is present in an amount of between 0.05 and 2 parts byweight per 100 parts by weight of halogenated polymer. Preferably, theamount of silylated compound is between 0.05 and 1 part by weightrelative to the same reference.

The silylated compounds may be obtained by any means known to personsskilled in the art.

By way of example, it is possible to react the β-dicarbonyl compoundwith the halosilane, optionally in the presence of an amino base (suchas pyridine, imidazole), preferably in a stoichiometric quantity,because its role is to capture the hydrochloric acid formed.

This reaction generally takes place in the presence of a solvent chosenfrom ethers, aliphatic hydrocarbons (pentane, for example), or aromatichydrocarbons (toluene, for example).

Furthermore, the halosilane and the β-dicarbonyl compound areadvantageously used in a stoichiometric quantity, even in the presenceof a slight excess of halosilane.

It is likewise recommended to carry out the reaction under an anhydrousatmosphere, such as rare gases (such as argon) and nitrogen, inter alia.

The reaction temperature may be easily determined by persons skilled inthe art. Purely by way of illustration, the temperature varies between20 and 100° C.

Once the reaction is complete, the silylated compound is separated fromthe reaction mixture, for example by distillation.

The stabilizing compound used for stabilizing halogenated polymers maycomprise, in addition, at least one organometallic stabilizer comprisinga metal chosen from groups IIA, IIB and IIIB of the Periodic Table ofElements (which appeared in the bulletin de la société chimique deFrance—January 1966). In particular, calcium, barium, zinc, cadmium,lead and tin are suitable, as well as combinations thereof. Preferably,the stabilizer comprises at least calcium, zinc or mixtures thereof.

The organometallic stabilizers are chosen more particularly from themetal salts of saturated or unsaturated aliphatic, aromatic ornonaromatic carboxylic acids optionally carrying one or more hydroxylgroups, or alternatively chosen from aromatic or nonaromaticalcoholates.

By way of examples of such compounds, there may be mentioned salts ofmaleic, acetic, diacetic, propionic, hexanoic, 2-ethylhexanoic,decanoic, undecanoic, lauric, myristic, palmitic, stearic, oleic,ricinoleic, behenic (docosanoic), hydroxystearic, hydroxyundecanoic,benzoic, phenylacetic, para-tert-butylbenzoic and salicylic acids,phenolates, alcoholates derived from naphthol or phenols substitutedwith one or more alkyl radicals, such as nonylphenols.

In the case of a zinc-based organometallic stabilizer, the stabilizingcomposition advantageously has a content of organometallic stabilizer ofbetween 10 and 200 ppm, expressed as metal, relative to the weight ofhalogenated polymer. Preferably, the content of organometallicstabilizer is between 30 and 150 ppm, expressed as metal, relative tothe weight of halogenated polymer. It should be noted that these rangesmore particularly represent the total content of this metal present inthe stabilizing composition.

In the case of an organometallic stabilizer comprising calcium, thecomposition advantageously has a content of organometallic stabilizer ofbetween 30 and 600 ppm, expressed as metal, relative to the weight ofhalogenated polymer. Here again, it should be noted that these valuesmore particularly represent the total content of this metal present inthe stabilizing composition.

The stabilizing composition may comprise other conventional additives inthe field, or may be used with conventional additives in the field.

By way of additives which may be envisaged, there may be mentioned freeor chelated β-diketones whose boiling point is at least 30° C., moreparticularly at least 60° C., preferably at least 80° C., higherrelative to the working temperature of said halogenated polymer.

By way of example of such compounds, there may be mentioned mostparticularly octanoylbenzoyl-methane, stearoylbenzoylmethane,dibenzoylmethane or alternatively acetylbenzoylmethane.

For the compounds provided in the form of a chelate, and thereforecombined with a metal, the latter is usually zinc, calcium, aluminum,magnesium or lanthanum; calcium and zinc being preferred.

Furthermore, these products may be used in purified or unpurified form.

The following commercial products may be advantageously used: Rhodiastab50®, Rhodiastab X5®, Rhodiastab 83®, Rhodiastab X2®, Rhodiastab X7®,Rhodiastab X9®, marketed by Rhodia Chimie.

The free or chelated β-diketone content is usually between 0.05 and 1part by weight per 100 parts by weight of halogenated polymer. It shouldbe noted that if a β-diketone chelated with calcium or zinc is present,the content of this chelated compound is such that the total zinc orcalcium content is in the ranges indicated above.

The polyols comprising 2 to 32 carbon atoms and having two to ninehydroxyl groups, may also be used as additives in this field.

Among these compounds, there may be mentioned C₃-C₃₀ diols such aspropylene glycol, butanediol, hexanediol, dodecanediol, neopentylglycol, polyols such as trimethylolpropane, pentaerythritol,dipentaerythritol, tripentaerythritol, xylitol, mannitol, sorbitol,glycerine and mixtures of oligomers of glycerine having a degree ofpolymerization of 2 to 10.

Another family of polyols which may be suitably used consists ofpartially acetylated polyvinyl alcohols.

It is likewise possible to use hydroxylated compounds comprisingisocyanurate groups, alone or in combination with the abovementionedpolyols, such as for example tris(2-hydroxyethyl) isocyanurate.

The quantity of polyol used is generally between 0.05 and 5 parts byweight per 100 parts by weight of polymer. More particularly, it is lessthan 2 parts by weight per 100 parts by weight of halogenated polymer.

It is possible to optionally incorporate into the formulation, or to usewith the latter, compounds of the organic phosphite type, such as forexample trialkyl, aryl, triaryl, dialkylaryl or diarylalkyl phosphites,for which the term alkyl denotes hydrocarbon groups of C₈-C₂₂monoalcohols or polyols, and the term aryl denotes aromatic groups ofphenol or of phenol substituted with C₆-C₁₂ alkyl groups.

It is similarly possible to use inorganic phosphites such as calciumphosphites. For example, compounds of the Ca(HPO₃).(H₂O) type andphosphite—hydroxy—aluminum—calcium complexes may be used.

The content of additive of this type is usually between 0.1 and 2 partsby weight per 100 parts by weight of halogenated polymer.

The stabilizing composition may comprise, or may be used with, compoundsof the epoxide type. These compounds are generally chosen fromepoxidized polyglycerides, or epoxidized fatty acid esters, such asepoxidized linseed, soybean or fish oils.

The quantity of compounds of this type usually varies between 0.5 and 10parts by weight per 100 parts by weight of halogenated polymer.

Among the conventional additives, there may likewise be mentionedaluminum and/or magnesium sulfates and/or carbonates, of thehydrotalcite type in particular. They are more particularly compounds offormula Mg_(1-x)Al_(x)(OH)₂A^(n−) _(x/n)-mH₂O, in which x is between 0excluded and 0.5, A^(n−) represents an anion such as carbonate inparticular, n varies from 1 to 3 and m is positive. It should be notedthat it is possible to use products of this type which have undergone asurface treatment with an organic compound. There would likewise be nodeparture from the context of the present invention by using a productof the hydrotalcite type doped with zinc, which has optionally undergonea surface treatment with an organic compound. Among the products of thistype, there may be mentioned most particularly Alcamizer® 4 (marketed bythe company Kyowa).

It is also possible to use essentially amorphous compounds of formula(MgO)_(y), Al₂O₃, (CO₂)_(x), (H₂O)_(z), in which x, y and z verify thefollowing inequalities: 0<x≦0.7; 0<y≦1.7 and z≧3. These compounds are inparticular described in patent application EP 509 864. Moreover, thecompounds called catoites of formula Ca₃Al₂(OH)₁₂ or Ca₃Al₂(SiO)₄(OH)₁₂may be used.

It is likewise possible to use additives of the synthetic, crystallinealkali metal aluminosilicate type, having a water content of between 13and 25% by weight, having the composition 0.7-1M₂O.Al₂O₃.1.3-2.4SiO₂ inwhich M represents an alkali metal such as in particular sodium.Zeolites of the NaA type, as described in patent U.S. Pat. No.4,590,233, are particularly suitable.

The content of this type of compound generally varies between 0.1 and 5parts by weight per 100 parts by weight of halogenated polymer.

The compositions may also comprise (or may be used with) titaniumdioxide, preferably in rutile form, optionally having undergone asurface treatment, preferably of the mineral type.

Generally, the particle size of the titanium dioxide is between 0.1 and0.5 μm.

Among the suitable titanium dioxides, there may be mentioned, interalia, the titanium dioxides Rhoditan® RL18, Rhoditan® RL90, marketed byRhodia Chimie, the titanium dioxides KRONOS 2081® and 2220® marketed byKronos.

The formulations based on halogenated polymers may likewise compriseother white or colored pigments. Among the colored pigments, there maybe mentioned in particular cerium sulfide.

It should be noted that the quantity of pigment introduced into theformulation varies within wide limits and depends in particular on thecoloring power of the pigment and on the final coloration desired.However, by way of example, the quantity of pigment may vary from 0.1 to20 parts by weight per 100 parts by weight of halogenated polymer,preferably from 0.5 to 15 parts by weight relative to the samereference.

Other conventional additives may make up the formulation, according tothe application for which it is intended.

As a general rule, the formulation may comprise phenolic antioxidants,anti-UV agents such as 2-hydroxybenzophenones, 2-hydroxybenzotriazolesor sterically hindered amines, usually known by the term Hals.

The content of this type of additive generally varies between 0.05 and 3parts by weight per 100 parts by weight of halogenated polymer.

If necessary, it is also possible to use lubricants which willfacilitate the use, chosen in particular from glycerol monostearates oralternatively propylene glycol, fatty acids or esters thereof, themontanate waxes, the polyethylene waxes or their oxidized derivatives,paraffins, metal soaps or functionalized polymethylsiloxane oils such asfor example γ-hydroxypropylenated oils.

The quantity of lubricant entering into the formulation based on ahalogenated polymer generally varies between 0.05 and 2 parts by weightper 100 parts by weight of halogenated polymer.

It is also possible to use plasticizers chosen from alkyl phthalates.The compounds most generally used are chosen from di(2-ethylhexyl)phthalate, esters of linear C₆-C₁₂ diacids, trimellitate oralternatively phosphate esters.

The quantity of plasticizer used in the formulations varies within abroad range, according to the desired rigid or supple character. As aguide, the content varies from 0 to 100 parts by weight per 100 parts byweight of halogenated polymer.

As regards the halogenated polymers which may be stabilized by thecomposition comprising at least one silylated compound, the latter aremore especially chlorinated polymers.

The invention is particularly well suited for stabilizing formulationsbased on polyvinyl chloride (PVC).

The expression polyvinyl chloride is understood to mean compositions inwhich the polymer is a homopolymer of vinyl chloride. The homopolymermay be chemically modified, for example by chlorination.

Numerous copolymers of vinyl chloride may also be stabilized using thecomposition according to the invention. They are in particular polymersobtained by copolymerization of vinyl chloride with monomers having anethylenically polymerizable bond, such as for example vinyl acetate,vinylidene chloride; maleic and fumaric acids or esters thereof; olefinssuch as ethylene, propylene, hexene; acrylic or methacrylic esters;styrene; vinyl ethers, such as vinyl dodecyl ether.

Usually, the copolymers contain at least 50% by weight of vinyl chlorideunits and preferably at least 80% by weight of such units.

PVC alone or as a mixture with other polymers is the chlorinated polymermost widely used in the stabilized formulations according to theinvention.

In general, any type of polyvinyl chloride is suitable, regardless ofits mode of preparation. Thus, the polymers obtained for example usingprocesses in bulk, in suspension or in emulsion may be stabilized usingthe composition according to the invention, regardless of the intrinsicviscosity of the polymer.

The working of the halogenated polymer comprising the stabilizingcomposition may be carried out by any means known to persons skilled inthe art.

It is thus possible to incorporate the various constituents into thepolymer individually or alternatively after having prepared beforehand amixture of several of these constituents.

Conventional methods of incorporation are perfectly suitable forproducing the formulation based on PVC.

Thus, and solely as a guide, it is possible to carry out this operationin a mixer provided with a system of paddles and counter-paddlesoperating at high speed.

Generally, the mixing operation is performed at a temperature of lessthan 130° C.

Once the mixture has been prepared, the composition is worked accordingto the customary methods in the field such as injection,extrusion-blowing, extrusion, calendering or alternatively molding byrotation.

The temperature at which the working is performed varies in general from150 to 220° C.

1. The use, in a stabilizing composition for halogenated polymers, of atleast one silylated compound of the following formula:(R¹)_(4-x)—Si[O—C(R²)═CH—C(═O)(R³)]_(x) in which formula R¹, which areidentical or not, represent an aliphatic or aromatic radical; saidradicals being chosen such that the silylated compound has a boilingpoint at least 30° C. higher relative to the working temperature of saidpolymer; R³ represents an aliphatic radical R or a radical —OR′; R², Rand R′, which are identical or not, represent a linear or nonlinearaliphatic radical comprising 1 to 10 carbon atoms, or an aromaticradical, preferably comprising 6 carbon atoms, optionally substitutedwith at least one aliphatic radical comprising 1 to 10 carbon atoms; xequals 1 or
 2. 2. The use as claimed in the preceding claim,characterized in that the radical R¹ is an alkyl radical comprising 1 to10 carbon atoms, or an aromatic radical comprising 6 carbon atoms,optionally substituted with at least one alkyl radical comprising 1 to10 carbon atoms.
 3. The use as claimed in claim 2, characterized in thatR¹, which are identical or not, represent a methyl, ethyl, propyl,isopropyl, butyl and isomers, pentyl and isomers, hexyl and isomers,phenyl, toluyl or xylyl radical.
 4. The use as claimed in one of thepreceding claims, characterized in that R², R or R′, which are identicalor not, each represent an alkyl radical comprising 1 to 10 carbon atoms.5. The use as claimed in one of the preceding claims, characterized inthat R³ represents a radical R chosen from alkyls comprising 1 to 10carbon atoms.
 6. The use as claimed in one of the preceding claims,characterized in that the content of silylated compound is between 0.05and 2 parts by weight per 100 parts by weight of halogenated polymer,preferably between 0.05 and 1 part by weight relative to the samereference.
 7. The use as claimed in one of the preceding claims,characterized in that the composition comprises at least oneorganometallic stabilizer comprising a metal chosen from groups IIA, IIBand IIIB of the Periodic Table of Elements, preferably calcium, zinc ora combination thereof.
 8. The use as claimed in claim 7, characterizedin that the organometallic stabilizer is chosen from the metal salts ofsaturated or unsaturated aliphatic, aromatic or nonaromatic carboxylicacids optionally carrying one or more hydroxyl groups, or aromatic ornonaromatic alcoholates.
 9. The use as claimed in either of claims 7 and8, characterized in that the stabilizing composition has a content ofzinc-based organometallic stabilizer of between 10 and 200 ppm,preferably between 30 and 150 ppm, expressed as metal, relative to theweight of halogenated polymer; this content representing the totalquantity of this metal in the stabilizing composition.
 10. The use asclaimed in either of claims 7 and 8, characterized in that thestabilizing composition has a content of calcium-based organometallicstabilizer of between 30 and 600 ppm, expressed as metal, relative tothe weight of halogenated polymer; this content representing the totalquantity of this metal in the stabilizing composition. R¹, which areidentical or different, represent an aliphatic or aromatic radical; saidradicals being chosen such that the silylated compound has a boilingpoint at least 30° C. higher relative to the working temperature of saidpolymer; R³ represents an aliphatic radical R or a radical —OR′; R², Rand R′, which are identical or different, represent a linear ornonlinear aliphatic radical comprising 1 to 10 carbon atoms, or anaromatic radical, optionally substituted with at least one aliphaticradical comprising 1 to 10 carbon atoms; and x equals 1 or
 2. 12. Thestabilizing composition as claimed in claim 11, wherein the radical R¹is an alkyl radical comprising 1 to 10 carbon atoms, or an aromaticradical comprising 6 carbon atoms, optionally substituted with at leastone alkyl radical comprising 1 to 10 carbon atoms.
 13. The stabilizingcomposition as claimed in claim 12, wherein R¹ represent a methyl,ethyl, propyl, isopropyl, butyl, butyl isomers, pentyl, pentyl isomers,hexyl, hexyl isomers, phenyl, toluyl or xylyl radical.
 14. Thestabilizing composition as claimed in claim 1 1, wherein R², R or R¹,which are identical or different, each represent an alkyl radicalcomprising 1 to 10 carbon atoms.
 15. The stabilizing composition asclaimed in claim 11, wherein R³ represents a radical R being an alkylcomprising 1 to 10 carbon atoms.
 16. The stabilizing composition asclaimed in claim 11, wherein the content of silylated compound isbetween 0.05 and 2 parts by weight per 100 parts by weight ofhalogenated polymer.
 17. The stabilizing composition as claimed in claim16, wherein the content is between 0.05 and 1 part by weight.
 18. Thestabilizing composition as claimed in claim 11, further comprising atleast one organometallic stabilizer comprising a metal of groups IIA,IIB or IIIB of the Periodic Table of Elements.
 19. The stabilizingcomposition as claimed in claim 18, wherein said metal is calcium, zincor a combination thereof.
 20. The stabilizing composition as claimed inclaim 18, wherein the organometallic stabilizer is a metal salt ofsaturated aliphatic acid, unsaturated aliphatic acid, aromaticcarboxylic acid, nonaromatic carboxylic acid, optionally carrying one ormore hydroxyl groups, aromatic alcoholate or nonaromatic alcoholate. 21.The stabilizing composition as claimed claim 19, wherein the stabilizingcomposition has a content of zinc-based organometallic stabilizer ofbetween 10 and 200 ppm, expressed as metal, relative to the weight ofhalogenated polymer; this content representing the total quantity ofthis metal in the stabilizing composition.
 22. The stabilizingcomposition as claimed in claim 19, wherein the stabilizing compositionhas a content of calcium-based organometallic stabilizer of between 30and 600 ppm, expressed as metal, relative to the weight of halogenated